The typical vertebra has a thick anterior bone mass called the vertebral body, with a neural (vertebral) arch that arises from the posterior surface of the vertebral body. The central portions of adjacent vertebrae are supported by intervertebral discs. The spinal disc and/or vertebral bodies may be displaced or damaged due to trauma, disease, degenerative defects, or wear over an extended period of time. One result of this displacement or damage to a spinal disc or vertebral body may be chronic back pain. In many cases, to alleviate back pain from degenerated of herniated discs, the disc is removed along with all or part of at least one neighboring vertebrae and is replaced by an implant that promotes fusion of the remaining bony anatomy. However, the success or failure of spinal fusion may depend upon several factors. For instance, the spacer or implant used to fill the space left by the removed disc and bony anatomy must be sufficiently strong to support the spine under a wide range of loading conditions. The spacer should also be configured so that it likely to remain in place once it has been positioned in the spine by the surgeon. Additionally, the material used for the spacer should be biocompatible and should promote bone growth and integration.
An additional support system, such as a system including plates and/or screws, is typically used in combination with spacers to further stabilize the spine during the fusion process. These devices, commonly referred to as bone fixation plating systems, typically include one or more plates and screws for aligning and holding vertebrae in a fixed position with respect to one another. Plating systems that are independent of the spacers often present additional failure modes for the spinal fusion process. For example, the screws may loosen over time, or the hardware may fail due to other means, such as breakage.
Similar problems arise with medical implants which integrate with hard tissue at other locations in the body. Such medical implants may be used, for example, in a knee, shoulder, elbow, wrist, ankle, hip, or finger.
Given the problems discussed above, there is a need for a spine stabilization system that promotes fusion of adjacent vertebrae while at the same time providing stabilization of the spinal area where fusion occurs. Thus, there is a need for a spinal implant or bone graft that addresses the problems associated with using separate spacers and stabilization systems.
More broadly, there is a need for medical implants used without separate stabilization systems that are useful for fixation and integration with hard tissue at other locations in the body. Accordingly, one aspect of the invention is to provide such an implant and a method for using the same. Other embodiments will be apparent from the following description of the invention.